Aomori Gyosai Center is the place to try nokkedon, the city's do-it-yourself seafood bowl. Buy rice and tickets, then trade the tickets at market stalls for scallops, tuna, salmon roe, sea urchin, crab, and whatever else looks best that morning.
It is simple, fun, and very Aomori: cold-water seafood, no ceremony, and a good lunch within walking distance of the station. Go before the late afternoon; markets are morning places even when posted hours run longer.